Magnet apparatus



Jan. 16, 1962 w, KANE T AL 3,017,544

MAGNET APPARATUS Filed March 19, 1954 3 Sheets-Sheet 1 w MAM v E a AAA [:4

N T, Q H l I N o 0 5 will IL a {a U E M a H: N o N link M w l I P44 P/W W. KANE FOEEESTAJVELSOA/ EMEEY H. 206525 lA/l/E/VTOR S Jan. 16, 1962 R. w. KANE ETAL 3,017,544'

MAGNET APPARATUS Filed March 19, 1954 3 Sheets-Sheet 2 FOEEEST A. NELSON EMEEY H. Ease-2s I In PAL/ H W. KANE L: nvvewroes ATTORNEY Jan. 16, 1962 MAGNET APPARATUS Filed March 19, 1954 R. W. KANE ETAL 3 Sheets-Sheet 3 EAL PH 'V- K N 5 F022 as 7-A NELSON EMEES/ H. EOGE'ES INVENTORS 3,017,544 MAGNET APPARATUS Ralph W. Kane and Forrest A. Nelson, Atherton, and Emery H. Rogers, Palo Alto, Calif., assignors to Varian Associates, San Carlos, Calif., a corporation of California Fiied Mar. 19, 1954, Ser. No. 417,482 8 Claims. (Cl. 317-458) This invention relates in general to magnets and more particularly to a novel magnet structure which provides extensive versatility in operation while maintaining precision and stability.

- In many applications of permanent and electromagnets there has long existed the need for an instrument in which the magnet gap spacing may be readily varied for controllably varying field strength and gap room and in which precise parallelism of the pole faces may be maintained so as to retain maximum field uniformity. Also, it is desired that pole pieces of varied sizes and configurations may be interchangeably utilized so as to regulate gap spacing, field strengths, and/or field patterns, and in which the physical position of the magnet structure may be easily changed relative to the surroundings without undue exertion so that the magnet portions such as the gap may be made more readily accessible.

It is, therefore, an object of the present invention to provide a versatile magnet structure which will meet'the above requirements without sacrificing the precision or stability obtainable in rigidly fixed magnet structures of relatively limited versatility.

A feature of the present invention is the provision of a novel split yoke structure whereby the magnet gap may be varied in length without any adjustment to the pole pieces or pole caps themselves.

Another feature of this invention is the provision, while utilizing the above feature, of variable sized shims for use between the split yokes to maintain the yoke substantially as a unitary structure, the shim being held in place by novel retaining apparatus.

Another feature of the present invention is the provision of a novel magnet apparatus wherein the pole pieces are slidably mounted in sleeves secured in the yoke, the gap being variable by sliding the pole pieces back and forth in the sleeves.

Another feature of this invention is the provision of a novel shimming means for tilting the pole faces into parallelism.

Another feature of the present invention is the provision of a novel apparatus for tightly securing removable pole caps on the associated pole pieces whereby a close fit between the piece and the cap is assured and thus the proper gap spacing and pole face parallelism produced.

Still another feature of the present invention is the provision of a novel method and apparatus for shimming the circumferential edges of a pole cap or face so as to maintain uniformly flat surfaces on the pole face and shim even when the shim is extremely thin.

Another feature of the present invention is the provision of a novel magnet mounting structure which permits both gap adjusting movement of the yokes relative to one another and rotational movement of the entire magnet structure relative to the mounting structure.

These and other objects, features, and advantages of the present invention will be evident upon a perusal of the following specification and claims taken in connection with the accompanying drawings wherein,

FIG. 1 shows in plan view one embodiment of the novel magnet structure of the present invention,

FIG. 2 is an end view from the right of the magnet structure shown in FIG. 1,

atent 3 ,017,544 Patented Jan. 16, 1962 FIG. 3 is a longitudinal cross section view of the magnet apparatus of FIG. 1,

FIG. 4 is an enlarged fragmentary section view of that portion of the magnet circled by line 44 in FIG. 3 showing the novel Rose shim construction,

FIG. 5 is an end view of the apparatus of FIG. 4,

FIG. 6 is a section view of another embodiment of the novel shimming apparatus,

FIG. 7 is an enlarged fragmentary section view of a portion of the magnet apparatus of FIG. 3 indicated by section line 77, and

FIG. 8 is a longitudinal section view of a gap-adjusting magnet embodying the present invention.

Referring now to the drawings, especially FIGS. 1, 2 and 3, there is shown an electromagnet which embodies certain novel features of this invention. This electromagnet comprises a yoke structure including two separable U-shaped yoke halves 1 and 2 which are arranged for relative axial movement to vary the magnet gap, yoke half 1 moving relative to the remainder of the magnet structure. The opposed surfaces of the legs of the yoke halves 1 and 2 are carefully machined to insure parallelism and'proper contact. Yoke 2 is rotatably mounted by means of a hub portion 3 in the bore of a trunnion 4, the trunnion being mounted on a solid support or base 5 as by screws 6. Integral with the two leg portions of yoke half 2 are mounting bosses or protrusions 7, 8 and 9, these protrusions having cylindrical bores extending therethrough.

Rotatably mounted in the opposite trunnion 11 is an elongated bracket 12 having bores in the opposite ends thereof. A pair of partially threaded support rods 13 and 14 are fixedly mounted in the bores in said bracket by means of their turned down ends and jamming nuts 15 and 16. The opposite ends of these support rods 13 and 14 are fixedly secured within the bores of the protruding portions 7 and 9, respectively, as by pins 7' and 9', the rod 14 also extending through boss 8. The yoke half 1 also has bosses or protruding portions 17, 18 and 19 each having bores therethrough, said support rods 13 and 14 passing through the bores in said portions 17 and 18 and 19, respectively. The weight of the yoke halves and associated apparatus is carried by the two trunnions 4 and 11, the bracket 12 and the support rods 13 and 14.

Mounted on the support rod 13 on opposite sides of protrusion 17 are threaded nuts 21 and 22. Mounted on support rod 14 between protrusions 18 and 19 is a threaded nut 23. The yoke half 1 may be moved toward or away from the yoke half 2 by means of the nuts 21, 22 and 23. By backing nuts 21 and 23 from the portions 17 and 18 and by subsequently turning nuts 22 and 23 in engagement with the protrusions 17 and 19, the yoke 1 may be moved away from yoke 2 and in a similar reverse manner the yoke 1 may be moved toward yoke 2. With the yoke split, suitable yoke spacers 26 may be inserted between the yoke halves such that when the halves are again brought toward each other, the spacers are compressed in the yoke and maintai n the field gap space at any desired length dependent on the size of the selected yoke spacers while at the same time completing the core path around the gap space. The yoke spacers 26 are carefully machined so that true parallelism of the pole faces is maintained throughout the range of gap spacings.

The rectangular yoke spacers are slightly wider than the yoke halves (see FIG. 7) and thus extend out from both sides of the yoke, the protruding portions of the spacers having aligned bores therein. Extending from both sides of the four yoke legs are small integral mounds or bosses 24, these mounds having narrow channels therein for accommodating spacer supporting rods 25. These rods 25 extend through thebores in the rectangular shaped yoke spacers 26, the boresand mounds 24 being so arranged that the rods are held irr a bowed tension bearing the yoke is split until the yoke half 1 may be moved toward yoke half 2 to compress the yoke spacers 26 therebe-- tween.

Fixedly secured on the yoke halves l and 2 as by means. of screws 27 are pole pieces 28 and 29, respectively. Slipped over these pole pieces 28 and 29 are the energizing coils 31 and 32, respectively, the coils being secured to the yoke halves by means of protruding tabs 33 and screws 34. Removable substantially cylindrical pole caps 35 and 36 are secured against the pole pieces 23? and 29' by means of draw bars or rods 37 and 38, respectively. Draw bar 37 is threaded at one end into athreaded bore in the inner surface of pole cap 35, this draw bar extending through cylindrical bores in the pole piece 28 and yoke: half 1. The outer end of the draw bar is turned down and threaded at the extreme outer end thereof. The outer end 39 of the bore in the yoke 1 is threaded and a pole cap locking screw 41 is threaded into this bore. A cap nut 42 is securely tightened over the threadedend of the draw bar 37. To draw the pole cap 35 tightly against the pole piece 28, the pole cap lock screw 41 is'turnedout from the yoke, bearing against the cap nut 42 and: thus forcefully moving the draw bar 37 to the right asviewed in FIG- 3 and thus pressing the pole cap 35 against the pole piece 28.. The apparatus for securing pole cap 36 to: the associated pole piece 29 is the same as described above for pole. cap 35.

In utilizing this magnet it can be seen that the air gap" between the pole caps 35 and 36 may be varied by re-- placing the pole caps with caps of a different thickness and shape or it may be varied by separating the two yoke halves 1 and 2 and changing the thicknesses of the yoke spacers between the two halves or a combination of these two methods may be used. The spacer rod 25 assures. that the yoke halves may be split apart without having the spacers fall from between them, yet providing that the spacers may be easily and rapidly removed and replaced with other yoke spacers.

Also, because of the novel mounting structure for this: split yoke type magnet, the whole magnet may be rotated about its longitudinal axis in the bores of the trunnions. 4 and 11 through any desired angle, such as 90 as shown; in FIG. 2.

A typical magnet made in accordance with the present invention has a pole diameter of 6 inches, pole caps of 6 inch diameter and 2 inch thickness. The minimum air" gap is .25 inch and the maximum air gap with the yoke.- halves split apart is 6 inches. By use of various sized yokespacers, the air gap is varied between the maximum and the minimum in steps of .25 inch.

This novel magnet structure, in addition to providing removable pole caps, also provides a novel method and apparatus for shimming the pole faces whereby various modifications of the magnetic field strength and pattern across the air gap may be obtained. The particular shimming employed is of the Rose shim type, so named because of its introduction by M. E. Rose in The Physical Review, vol. 53, page 715 (1938), where the circumferential edge of the pole face is raised slightly to provide a raised annular band with respect to the main portion of the pole face. In a known method for producing a Rose shim of thisv type, the inner diameter portion of the face is turned. down so as to leave the raised annular band portion around the circumference of the face. This method is not satisfactory'because of the extreme difficulty in getting a true surface flatness of the turned down surface portion. One embodiment of the Rose shimmed pole face of the present invention is shown in FIGS. 3, 4 and and is produced by turning down the outer periphery of the pole caps 55 and 36 so as to produce annular recesses or steps around the pole caps. An annular member 46'is them machined to snugly fit within each annular recess portion and is secured to the pole cap by means of screws 47. The face of main pole cap such as 36 and the annular ring portion 46 may then be surface ground together to produce the true surface flatness needed for the main pOle face and shim surfaces. The shimming of this annular ring 46 is then accomplished by placing an annular member 48 of shim material of any desired thickness, for example, 5 mils, under the annular member 46 and tightening the screws 47 to compress the shim 48 between the annular member and the ledge of the recess in the main pole cap. The shim 48 is compressed completely flat with complete elimination of buckling regardless of the thinness of the shim material. If an' attempt were made to secure such thin shims directly on the pole face surface, buckling of the shim would destroy any benefits derived from the shimming. But by compressing the shim material between two solid, unyielding members 36 and 46, this difficulty is eliminated. Thus the height of the annular member 46 with respect to the main pole face may be of any desired value from zero on up in steps of thousandths of an inch without affecting the parallelism of the faces of the member 46 and the main pole cap 36.

There is shown in FIG. 6 another embodiment of the novel pole shimming means where the pole caps 51 are tapered to a smaller diameter, the annular member 52 being tapered to conform to the tapered surface of the v pole cap. A thin shim 52' is secured between the pole cap 51 and the member 52.

Shown mounted on the yoke half 1 in FIG. 2 is the manifold 49 and associated copper tubing 49 which car ries cooling liquid such as water through the coil portion of this magnet for maintaining the magnet at a cool operating temperature.

In FIG. 8 is shown a novel gap-adjusting electromagnet apparatus which comprises a U-shaped yoke 53 having aligned bores extending through the opposite legs thereof. Fixedly secured in these bores are cylindrical sleeves 54 and 55, the sleeves having annular flanges 54 and 55' on their outer ends. Extending through threaded bores in the flanges 54 and 55' are shimming screws 56, the ends of which bear against the surface of the legs of the yoke 53. A plurality of these shimming screws are equally spaced around the flanges '54 and 55' and, by turning these screws in or out, the sleeves 54 and 55 may be slight- 1y tilted in the yokes in any direction relative to the iongitudinal axis and in this manner the associated pole faces may be adjusted to the desired parallelism. Mounting screws such as 57 secure the flanged sleeves to the yoke. Extending within the sleeves are pole pieces 58 and 59, the outer ends of which are threaded. Captured adjusting nuts 61 and 62 are threaded over these ends of the pole pieces, the nuts being held captured by the annular members 63 and 64 which are fastened to the flanges 54' and 55' by the screws 57. The adjusting nuts 61 and 62 may be rotated to cause the pole pieces 58 and 59 to slide within the sleeve in either direction and thus vary the gap spacing between the poles.

The magnet coils 68 and 69 are slipped over the sleeves 54 and 55, respectively, and are secured to the yoke 53 by suitable means not shown. The coils are thus fixedly secured to the magnet structure yet the associated pole pieces are secured to the magnet structure so as to be movable with respect to the coils, thus permitting rapid adjustment of the magnet gap by movement of the pole pieces without movement of the heavy coils.

A key and keyway 65 prevent rotation of the pole pieces. The pole caps 66 and 67 are secured to the pole pieces 58 and 59 in the same manner as those in FIG. 3.

Since many changes could be made in the construction of the novel magnet invention described above and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An electromagnet for producing a unidirectional magnetic field, comprising a pair of U-shaped magnetic flux conducting yoke halves, the ends of the pairs of legs of the two halves adapted to alignably engage whereby the two halves form a closed magnet yoke, a pair of magnet pole members, each of the pole members being mounted on a respective one of the yoke halves between the legs and extending inwardly toward each other in alignment and forming a magnetic field air gap therebetween, a pair of magnet energizing electric coil assemblies mounted on said magnet, each surrounding one of said pole members, means for producing adjustable relative movement between the two yoke halves whereby the two yoke halves may be separated to thereby increase the air gap spacing between the two pole members, and a pair of magnetic flux conducting spacers of equal thickness, each of which is adapted to be positioned in different ones of the two spaces between the ends of the aligned yoke legs, the yoke halves being moved together to clamp the spacers therebetween so as to provide a continuous flux path through the yoke.

2. A magnet as claimed in claim 1 including means coupling said spacers to said yoke legs for retaining the magnetic flux conducting spacers in position between the aligned yoke legs when the yoke halves are separated a distance greater than the thickness of the spacers.

3. A magnet as claimed in claim 2 wherein said retaining means includes a boss on each side of each leg of the two yoke halves, the yoke spacers extending beyond the sides of the yoke halves, the protruding ends of the spacers each having a bore extending therethrough, and a plurality of tension rods, each extending through one of the bores in the spacers, the ends of the tension rods passing over the bosses whereby the rods are maintained in a bent tension to hold the yoke spacers in the spaces between the ends of the yoke legs.

4. An electromagnet as claimed in claim 2 wherein said means for producing adjustable relative movement between said yoke halves comprises bosses extending outwardly from the outer surfaces of the four legs and having openings therein, a pair of support rods, one rod extending through the openings in the bosses on the legs on one side of the closed yoke and the other support rod extending through the openings in the bosses on the legs on the other side of the closed yoke, at least one of said halves sliding along said support rods whereby the two yoke halves may be separated to thereby increase the gap spacing between the two pole pieces, and mounting means including a pair of trunnions having mounting bores therein, a hub on one of the yoke halves rotatably mounted in the bore of one of said trunnions, an elongated bracket rotatably mounted at its midpoint in the bore of the other trunnion, means for securing one of the ends of each of said support rods to separate ones of the ends of the bracket, and means for securing the opposite ends of the support rods in the bosses on the legs of said one yoke half, the other yoke half being slidably mounted on the support rods between said one yoke half and the bracket.

5. A magnet for producing a unidirectional magnetic field comprising a pair of opposed circular pole members of solid magnetic material having substantially parallel pole faces with a magnetic field air gap therebetween, each pole member having an annular recess around the circumferential edge of the face thereof, separate annular Rose shim members of solid magnetic material adapted to fit around each face within the recess for controlling the magnetic field pattern across the gap, an annular shim of solid magnetic material adapted to fit in the recess under each of the annular Rose shim members, and means for securing the annular Rose shim members to the pole members whereby the annular shims are firmly compressed between the pole members and the annular Rose shim members to create a continuous magnetic flux path through each pole member and face and its associated annular shim and Rose shim member.

6. A combination as claimed in claim 5 wherein the thickness of the annular Rose shim member is equal to the depth of the recess, the surface of the Rose shim member extending a distance above the face of the pole member determined by the thickness of the shim.

7. A combination as claimed in claim 5 wherein said securing means comprises a plurality of screws equally spaced around the surface of the annular Rose shim member threaded into the pole member.

8. A magnet for producing a unidirectional magnetic field comprising a pair of opposed truncated cone magnet pole members of solid magnetic material having substantially parallel pole faces on the smaller diameter ends with a magnetic field air gap therebetween, each pole member having an annular recess around the circumferential edge of the face thereof, separate annular Rose shim members of solid magnetic material adapted to fit around each face within the recess for controlling the magnetic field pattern across the gap, the side of the annular Rose shim members tapering to substantially conform to the tapered side surface of the pole member, annular shims of solid magnetic material adapted to fit in the recesses under the annular Rose shim members, and means for securing the annular Rose shim members to the associated pole member whereby the annular shim is firmly compressed between the pole member and the annular Rose shim member to create a continuous magnetic flux path through each pole member and face and its associated annular shim and Rose shim member.

References Cited in the file of this patent UNITED STATES PATENTS 766,117 Rundle July 26, 1904 1,866,179 Sosinski July 5, 1932 2,162,465 Van Guilder June 13, 1939 2,394,070 Kerst Feb. 5, 1946 2,446,624 Allison Aug. 10, 1948 2,664,527 Reed Dec. 29, 1953 2,695,978 Scag Nov. 30, 1954 2,697,167 Kerst Dec. 14, 1954 2,819,431 Maxwell Jan. 7, 1958 FOREIGN PATENTS 587,821 Germany Nov. 9, 1933 487,068 Great Britain June 15, 1938 742,905 Germany Dec. 15, 1943 

